freebsd stable - Dec 2004 - FAILURE - WRITE_DMA timed out / FAILURE - WRITE_MUL timed out --- Problem

Hello,

during the last weeks I have some hangup-problems on my FreeBSD-5.3 
server. It seems to me that after the following error messages in syslog 
the server freezes and doesn't even respond to ping- and 
ssh-connection-attempts.

The messages in my /var/log/messages file:
Dec 16 17:34:03 susi kernel: ad0: TIMEOUT - WRITE_MUL retrying (2 
retries left) LBA=7026607
Dec 16 17:34:05 susi kernel: ad0: FAILURE - WRITE_MUL timed out

First it was "... WRITE_DMA ...". Then I disabled DMA and ACPI in 
loader.conf, but it doesn't help.

There was a WRITE_DMA-thread on this list already, but there wasn't a 
solution as far as I remember.


Does anyone know what this means and could these messages be the reasons 
for my server-freezes?

I also would like to compile a debug-kernel, if this would help anybody.


Thanks,
Kay Abendroth